The objective of this project is to study how the respiratory muscles affect regulation of breathing in newborn infants. We will concentrate on the effect of changes in lung volume on respiratory control and chest wall dynamics. We plan to examine changes in muscle activity observed with surface electromygrams of the diaphragm, abdominal muscles and intercostal muscles in newborn infants following increases in lung volume produced by both postural changes and application of continuous distending airway pressure (CDAP). In addition, we plan to study with magnetometers the configurational response of the chest wall to postural changes. We will also examine the EMG response of the diaphragm when rib cage expansion is curtailed during application of CDAP.